title: Performance evaluation of three assays for the detection of PR3-ANCA in granulomatosis with polyangiitis in daily practice.
abstract: BACKGROUND
  Anti-neutrophil cytoplasmic antibodies (ANCA) directed against proteinase 3 (PR3-ANCA) are a serological hallmark of small vessel vasculitis, particularly granulomatosis with polyangiitis (GPA). To increase their sensitivity, some ELISA employ the human native PR3 combined with a recombinant protein. Their specificity in daily practice is still to be defined. Our objective was to compare the performance for GPA diagnosis of three PR3-ANCA assays in daily practice.
  
  
  METHODS
  Seventy-eight consecutive patients' sera with suggestive IIF were included. All sera were tested with a routine Enzyme Linked Immuno adsorbant Assay (ELISA) employing a mixture of human native and human recombinant (hn+hr) PR3 (EUROIMMUN™) compared to two assays using immobilized purified human PR3 (QUANTA Lite(®) ELISA and QUANTA Flash(®) Chemiluminescence assay (CIA), INOVA Diagnostics). Clinical data including BVAS score were collected retrospectively.
  
  
  RESULTS
  Nineteen out of the 78 patients had GPA. The hn+hr PR3 ELISA had a good sensitivity (100%) but a lower specificity for the diagnosis of GPA (61.0%) than the assays using the sole native protein (hn ELISA: 81.4%, hn CIA: 69.5%). False positive results mainly consisted of patients with inflammatory bowel disease, who had a specific PR3-ANCA positivity assembly when coupling the assays. The antibody titers by human native PR3 assays, but not hn+hr assay, positively correlated with BVAS score.
  
  
  CONCLUSIONS
  These results highlight the need of a close collaboration between physicians and immunologists. Combining assays including last generation CIA employing human native antigens should improve the performance of GPA's diagnosis.
authors.affiliation: AP-HP, Centre de référence labellisé pour la prise en charge des cytopénies auto immunes de l'adulte, Service de Médecine Interne, CHU Henri Mondor, Créteil, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Noel
authors.forename: Chantal
authors.initials: C
authors.lastname: André
authors.forename: Djaouida
authors.initials: D
authors.lastname: Bengoufa
authors.forename: Catherine
authors.initials: C
authors.lastname: Dehoulle
authors.forename: Michael
authors.initials: M
authors.lastname: Mahler
authors.forename: Nicolas
authors.initials: N
authors.lastname: Limal
authors.forename: Bertrand
authors.initials: B
authors.lastname: Godeau
authors.forename: Sophie
authors.initials: S
authors.lastname: Hüe
mesh_terms: D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D014890:Granulomatosis with Polyangiitis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D006801:Humans; D008163:Luminescent Measurements; D008875:Middle Aged; D053146:Myeloblastin / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012680:Sensitivity and Specificity; D014657:Vasculitis / Q000097:blood / Q000175:diagnosis / Q000276:immunology
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D011994:Recombinant Proteins; D053146:Myeloblastin
keywords: ANCA; Detection methods; Granulomatosis with Polyangiitis; PR3